NAME

dkimproxy.in - SMTP proxy for verifying DKIM signatures

SYNOPSIS

  dkimproxy.in [options] LISTENADDR:PORT RELAYADDR:PORT
    smtp options:
      --conf_file=FILENAME
      --listen=LISTENADDR:PORT
      --relay=RELAYADDR:PORT
      --reject-error

    verification options:
      --reject-fail
      --hostname=HOSTNAME

    daemon options:
      --daemonize
      --user=USER
      --group=GROUP
      --pidfile=PIDFILE

  dkimproxy.in --help
    to see a full description of the various options

OPTIONS

--daemonize: If specified, the server will run in the background.
--group=GROUP: If specified, the daemonized process will setgid() to the specified GROUP.
--hostname=HOSTNAME: Overrides the hostname used in the Authentication-Results header. This header gets added to every verified message. Use this option if the hostname that appears is not fully qualified or you want to use an alternate name.
--pidfile=PIDFILE: Creates a PID file (a file containing the PID of the process) for the daemonized process. This makes it possible to check the status of the process, and to cleanly shut it down.
--reject-error: This option specifies what to do if an error occurs during verification of a message. If this option is specified, the message will be rejected with an SMTP error code. This will result in the MTA sending the message to try again later, or bounce it back to the sender (depending on the exact error code used). If this option is not specified, the message will be passed through with an error listed in the Authentication-Results header instead of the verification results.
The most common cause of an error when verifying a message is a DNS error when trying to retrieve a public key or sender policy.
--reject-fail: This option specifies what to do if verification fails and the sender signing policy says to reject the message. If this option is specified, the message will be rejected with an SMTP error code. This will result in the sending MTA to bounce the message back to the sender. If this option is not specified, the message will pass through as normal.
--user=USER: If specified, the daemonized process will setuid() to USER after completing any necessary privileged operations, but before accepting connections.

DESCRIPTION

dkimproxy.in listens on the IP address and TCP port specified by its first argument (the "listen" port), and sends the traffic it receives onto the second argument (the "relay" port), with messages getting verified and having an "Authentication-Results" header added to them.

EXAMPLE

For example, if dkimproxy.in is started with:

  dkimproxy.in --reject-fail --reject-error 127.0.0.1:10025 127.0.0.1:10026

the proxy will listen on port 10025 and send the verified messages to some other SMTP service on port 10026.

CONFIGURATION FILE

Parameters can be stored in a separate file instead of specifying them all on the command-line. Use the conf_file option to specify the path to the configuration file, e.g.

  dkimproxy.in --conf_file=/etc/dkimproxy_in.conf

The format of the configuration file is one option per line: name of the option, space, then the value of the option. E.g.

  # this is an example config file
  listen      127.0.0.1:10025
  relay       127.0.0.1:10026
  hostname    myhost.example.com
  reject_fail

is equivalent to

  dkimproxy.out --hostname=myhost.example.com --reject-fail \
                  127.0.0.1:10025 127.0.0.1:10026

AUTHOR

Jason Long